The scaling of green space coverage in European cities

Most people on the planet live in dense aggregations, and policy directives emphasize green areas within cities to ameliorate some of the problems of urban living. Benefits of urban green spaces range from physical and psychological health to social cohesion, ecosystem service provision and biodiversity conservation. Green space coverage differs enormously among cities, yet little is known about the correlates or geography of this variation. This is important because urbanization is accelerating and the consequences for green space are unclear. Here, we use standardized major axis regression to explore the relationships between urban green space coverage, city area and population size across 386 European cities. We show that green space coverage increases more rapidly than city area, yet declines only weakly as human population density increases. Thus, green space provision within a city is primarily related to city area rather than the number of inhabitants that it serves, or a simple space-filling effect. Thus, compact cities (small size and high density) show very low per capita green space allocation. However, at high levels of urbanicity, the green space network is robust to further city compaction. As cities grow, interactions between people and nature depend increasingly on landscape quality outside formal green space networks, such as street plantings, or the size, composition and management of backyards and gardens.     

转型中工业城市的公园绿地社会公平性研究——以东莞市东城街道为例

作为城市重要的生态空间,公园绿地为城市提供环境基础及景观保障,其资源的合理分配是社会公平的重要体现。提出公园绿地社会公平性新的内涵,即无论个体所处的人居环境条件如何,其获得的城市公园绿地质量应该平等。工业城市向服务型、创新型城市的转变是中国城镇发展的典型趋势,研究其公园绿地的社会公平性为城市更新改造与公共资源分配提供重要的科学依据。以东莞市东城街道为例,构建社会-经济-自然复合人居指标体系与公园质量评价体系,基于可达性模型与Pearson相关性系数对公平性进行测度。结果表明：由于区域更新强度及顺序不同,研究区的绿地布局存在不公平现象,居民享受的公园质量与小区的自然、经济要素具有一定的关联。转型中的工业城市高质量公园聚集于风景资源优越的高端居住区,其他公园质量普遍不佳。工业园区以及旧城区为公园服务盲区的主要聚集地。     

城市绿地对居民身心福祉的影响

城市绿地是人工与自然耦合的城市景观之一,是改善居民居住环境重要组成部分,更是提高居民身心健康的有效途径。以杭州主城区为研究对象,通过GIS技术对城市绿地遥感图像进行解译得到杭州主城区绿地空间布局图,同时,以人口密度为阻力要素,基于交通路网的500m网络距离可达范围内绿地数量和面积作为分类标准。通过对45个高、中、低不同档次的居民区进行问卷调查得到665份居民感知数据并进行统计整理。利用结构方程模型进行以绿地数量及游玩时间为标准的组间分析,区别不同组别的差异及其原因,分析城市绿地数量、面积,居民认知、动机,绿地吸引力等与居民身心健康福祉及满意度之间的关系。结果显示:城市绿地数量、居民游玩绿地次数时间等与居民福祉有显著的正向关系;居民对绿地作用的认知、去往绿地的动机进一步影响居民身心健康福祉;城市绿地的自身引力会激发居民去往绿地的积极性,从而增加去往绿地频次。另外,不同社会属性的个体对绿地需求不同,所产生的福祉效应及满意度也会有所差异。从增加居民区周围的街头绿地及邻里公园数量、提升绿地吸引力、提升居民对城市绿地作用的认知3个方面对城市绿地今后的发展规划提出建议。     

基于格兰杰因果实证的城市绿地与经济发展互动机制研究

城市绿地与经济发展的互动机制是社会-经济-自然复合生态系统和生态文明理论研究的重要内容。利用面板格兰杰因果关系检验和面板数据回归分析方法,对中国城市绿地与经济发展之间存在的因果互动关系开展实证研究。研究结果表明:(1)全国尺度上,城市建成区绿地率与人均GDP互为格兰杰原因,存在"正向循环反馈"的因果互动关系,即城市绿地水平的提高能够推动城市经济发展,而经济发展能够拉动城市绿地建设。城市绿地率与城市人均GDP的因果关系可以概括为"绿磁效应"(GME)和"需求效应"(GDE)。(2)区域尺度上,东部地区人均GDP与城市建成区绿地率存在单向格兰杰因果关系,人均GDP是城市绿地率增长的格兰杰原因,而城市绿地率不是人均GDP的格兰杰原因;(3)西部地区城市绿地率与人均GDP的交互强度最大,即西部"绿地-经济弹性"和"经济-绿地弹性"高于其他地区。东部地区通过扩大城市绿地率来提升经济发展的空间比较小,应着眼于提高城市绿地质量,中、西部地区城市绿地率较小,应在兼顾城市绿地质量的基础上提升城市建成区绿地率。本研究能够为城市绿地与经济发展的关系研究和城市生态规划与经济发展规划提供参考。     

斑块面积对城市绿地降温效应的影响研究进展

在气候变化和快速城市化的双重影响下,全球城市面临日益加剧的热岛效应。绿地能够有效改善城市热环境。城市土地资源紧缺,优化绿地布局,使有限面积的绿地发挥更大的降温效果具有重要的理论意义和实践价值。其中,如何设置绿地斑块大小则是优化绿地布局的首要考虑因素之一。从斑块和景观的尺度总结了现有绿地斑块大小对其降温效应影响的研究进展,结果表明：1）在斑块尺度,随着绿地斑块面积增加,绿地的降温效应相应增加,但增加的趋势为非线性变化,表现为温度随绿地斑块面积的增加先下降,后趋于平稳,表明可能存在降温效率（单位面积绿地降温能力）最强的斑块大小;2）在景观尺度,绿地斑块大小在空间上的配置对热环境的影响研究结果存在差异,尚无一致性定论。基于已有研究,本文指出了现有绿地斑块大小对其降温效应影响研究中的问题与不足：1）主要关注绿地斑块大小与温度的统计关系,缺乏对其具体影响过程和内在机制的深入探讨;2）更多关注地表温度,而对与人体舒适度和健康直接相关的其他热环境指标的研究较少;3）研究中缺少对城市中数量巨大,分布最广的小型绿地斑块的考量。未来的研究应加强从遮阴和蒸腾等降温过程深入解析绿地斑块大小对热环境影响的内在机理机制,从降温效率的角度,探讨是否存在最优的斑块大小,并进一步探讨绿地周围建筑环境对绿地斑块大小与其降温效应关系的影响,为优化城市绿地分布,改善城市热环境提供科学依据。     

Urban green space availability in European cities

Urban green space (UGS) availability has become an increasingly important aspect of planning and research because of the importance of green spaces for the wellbeing of urban residents. Municipalities across the European Union (EU) use different indicators in this area. Some cities provide per-capita threshold values for urban green space (UGS); some have recommendations regarding the minimum distance to green space while others have no recommendations at all. In this study, we assess green space availability in 299 EU cities according to land use and a population data grid. The results show a diverse picture across the EU. Southern European cities show below-average availability values, which may be explained by their low forest and tree cover and reflect the history of cities in Southern Europe. Comparatively, the above-average availability values in Northern European cities are a result of not only their biophysical conditions and the presence of rich forestland in general but also of Northern European attitudes toward urban living that naturally value having forests close to home.This assessment is complemented by a detailed case study analysis of two European cities ⿿ Berlin, Germany and ſódź, Poland. Results showed that this approach's explanatory power depends on the data used, scale of interest, resolution of data and estimated threshold value. By comparing results using different datasets and threshold values, we discuss opportunities and limitations for developing indicators of green space availability. We conclude that UGS availability is an important indicator to navigate urban complexity to improve human health and wellbeing but is only one component of the intricate social-ecological interactions within cities.     

基于MSPA分析方法的市域尺度绿色网络体系构建路径优化研究——以招远市为例

市域绿色空间是市域尺度内连接城市生态系统与自然生态系统的纽带,是维护市域整体生态系统稳定的基本保障。现阶段以中心城区为核心的城市绿地系统空间规划忽视了城市化过程中自然与城市之间发生的动态变化,忽视了市域绿色空间对城乡人居环境质量的决定作用。构建良好的市域尺度绿色空间体系,能够实现市域层面的生态环境稳定,协调城市化发展与自然资源保护之间的矛盾,对城市可持续发展有着积极意义。以招远市域绿色空间为研究对象,借助形态学空间格局分析(MSPA)方法,利用其研究尺度兼容性强、景观要素生态内涵明确、所得成果便于量化评估等优势特性,首先对招远市域绿色空间中的重要景观要素核心区、桥接区进行识别,并提取具有生态拓补潜力的景观要素孤岛作为未来绿色空间优化潜力节点的空间落点;其次选用可能联通性(PC)、斑块重要度等指数量化景观要素对绿色空间的重要度并进行评价分级;然后将核心区和潜力节点作为生态源,通过不同景观要素对物种流通的阻力构建消费阻力面,以最小路径方法得出场地内的潜力生态廊道;再次,通过通量分析定性不同生态斑块在生态过程中的功能角色,并借助核密度分析对潜力生态网络的发展趋势进行测度;最终以发展趋势较弱区域中对整体生态网络联通具有较高贡献度,并在生态过程中扮演踏脚石的一二级潜力节点斑块作为未来生态发展中的重要关键点进行生态质量提升,得出招远市域绿色空间发展结构,并提出科学的空间优化指引和发展建议。本研究可以为高度破碎化地区的绿色空间构建提供一定的理论依据,对我国城市化发展中其他地区的市域绿色空间构建也具有一定的参考和示范意义。     

基于电子导航地图POI的北京城区绿色空间服务半径分析

近年来,电子导航地图中的兴趣点（Point of Interest,POI）在城市地理与城市生态研究方面越来越受到重视。城市绿色空间对其居民的生产生活服务作用十分重要,城市绿地系统的配置是否科学对城市生态系统服务供需情况有着重要影响。利用北京城区五环以内的POI数据,采用核函数模拟出城市居民生产生活在空间分布上强弱程度的热力图,对该区域绿色空间实体不同半径服务区内的热力特征进行耦合分析。研究表明：北京市五环以内绿色空间实体500、750 m和1000 m典型服务半径的覆盖面分别占总面积的77.99%、91.55%和97.46%,从服务供给角度表现出空间分布格局相对均匀;但在绿色空间500 m服务半径内,仅覆盖了POI热力图中极高密度区中51.19%的地区,高密度区中54.78%的地区,中密度区中66.21%的区域,从服务需求角度表现出绿色空间分布格局明显不均衡。研究认为城市绿色空间在POI热度较高区域的主要商圈、人流密集区域匹配明显不足,需要通过增加绿地或疏解POI集中程度来缓解绿色空间供需矛盾。     

Public Parks and Wellbeing in Urban Areas of the United States

Sustainable development efforts in urban areas often focus on understanding and managing factors that influence all aspects of health and wellbeing. Research has shown that public parks and green space provide a variety of physical, psychological, and social benefits to urban residents, but few studies have examined the influence of parks on comprehensive measures of subjective wellbeing at the city level. Using 2014 data from 44 U.S. cities, we evaluated the relationship between urban park quantity, quality, and accessibility and aggregate self-reported scores on the Gallup-Healthways Wellbeing Index (WBI), which considers five different domains of wellbeing (e.g., physical, community, social, financial, and purpose). In addition to park-related variables, our best-fitting OLS regression models selected using an information theory approach controlled for a variety of other typical geographic and socio-demographic correlates of wellbeing. Park quantity (measured as the percentage of city area covered by public parks) was among the strongest predictors of overall wellbeing, and the strength of this relationship appeared to be driven by parks’ contributions to physical and community wellbeing. Park quality (measured as per capita spending on parks) and accessibility (measured as the overall percentage of a city’s population within ½ mile of parks) were also positively associated with wellbeing, though these relationships were not significant. Results suggest that expansive park networks are linked to multiple aspects of health and wellbeing in cities and positively impact urban quality of life.     

Spider communities in urban green patches and their relation to local and landscape traits

Urbanization and urban landscape characteristics greatly alter plant and animal species richness and abundances in negative and positive directions. Spiders are top predators, often considered to be sensitive to habitat alteration. Studies in urban environments frequently focus on ground-dwelling spiders or on spiders in built structures, leaving aside foliage spiders. Effects of habitat, landscape type and structure and local characteristics on spider species composition, richness and relative abundance were evaluated in urban green patches in a temperate city of South America. We also assess whether Salticidae could be an indicator group for the broader spider community in the urban environment. Spiders were sampled with a G-VAC (aspirator) in urban green patches in Córdoba city, Argentina, in urban, suburban and exurban habitats (18 sites; six per habitat) and local and landscape traits were assessed. Overall, the exurban was richer than the urban habitat, however, at the site level Salticidae richness and abundance (but not the total spider assemblage) were significantly lower in urban sites. Species composition moderately differed between urban and exurban sites. Results indicate that on urban green spaces a low impervious surface cover, a coverage of trees, herbaceous vegetation and a vertical structure of vegetation at least up to 1 m in height contribute to higher richness and abundance of spiders, Salticidae being more sensitive than the overall spider community to local effects. In addition, Salticidae richness can predict 74% of the total spider richness recorded and may be used as spider diversity bio-indicators in this climatic region.     

How should we grow cities to minimize their biodiversity impacts?

Urbanization causes severe environmental degradation and continues to increase in scale and intensity around the world, but little is known about how we should design cities to minimize their ecological impact. With a sprawling style of urban development, low intensity impact is spread across a wide area, and with a compact form of development intense impact is concentrated over a small area; it remains unclear which of these development styles has a lower overall ecological impact. Here, we compare the consequences of compact and sprawling urban growth patterns on bird distributions across the city of Brisbane, Australia. We predicted the impact on bird populations of adding 84 642 houses to the city in either a compact or sprawling design using statistical models of bird distributions. We show that urban growth of any type reduces bird distributions overall, but compact development substantially slows these reductions at the city scale. Urban‐sensitive species particularly benefited from compact development at the city scale because large green spaces were left intact, whereas the distributions of nonnative species expanded as a result of sprawling development. As well as minimizing ecological disruption, compact urban development maintains human access to public green spaces. However, backyards are smaller, which impacts opportunities for people to experience nature close to home. Our results suggest that cities built to minimize per capita ecological impact are characterized by high residential density, with large interstitial green spaces and small backyards, and that there are important trade‐offs between maintaining city‐wide species diversity and people's access to biodiversity in their own backyard.     

城市绿色空间可达性与居民分布的空间匹配与影响因素

城市居民的绿色空间可达性是衡量城市基础设施公平分配的指向标,关乎城市民生福祉。以宁波为研究区,基于高德地图路径规划Application Programming Interface(API)测度了绿色空间可达性,融合多源数据模拟了人口空间分布,分析了绿色空间可达性与人口分布的空间匹配状态,并采用地理探测器探讨其影响因素。研究表明：(1)宁波绿色空间可达性由各区中心向郊区衰减,高可达性空间占比不高,反映了绿色服务供给不足的现状。高可达性空间集中于三江口、鄞州新城、北仑城区和镇海老城区,低可达性空间则主要分布在东部郊区、西部山区和南部农业区。(2)宁波居民的绿色空间可达性在空间上表现为市中心高人口密度-高可达性和郊区低人口密度-低可达性的空间匹配特征,在规模上仅不及半数的居民享有15min绿色空间可达性,在乡镇尺度上呈现显著的城区—郊区二元类型分异。(3)城市居民绿色空间可达性受多重影响因子驱动,按照重要性依次为区位特征、人类活动、开发强度、社会经济和地形条件。     

Bird Richness and Abundance in Response to Urban Form in a Latin American City: Valdivia,Chile as a Case Study

There is mounting evidence that urban areas influence biodiversity. Generalizations however require that multiple urban areas on multiple continents be examined. Here we evaluated the role of urban areas on avian diversity for a South American city, allowing us to examine the effects of urban features common worldwide, using the city of Valdivia, Chile as case study. We assessed the number of birds and their relative abundance in 152 grid cells of equal size (250 m²) distributed across the city. We estimated nine independent variables: land cover diversity (DC), building density (BD), impervious surface (IS),municipal green space (MG),non-municipal green space (NG), domestic garden space (DG), distance to the periphery (DP), social welfare index (SW), and vegetation diversity (RV). Impervious surface represent 41.8% of the study area, while municipal green, non-municipal green and domestic garden represent 11.6%, 23.6% and 16% of the non- man made surface. Exotic vegetation species represent 74.6% of the total species identified across the city. We found 32 bird species, all native with the exception of House Sparrow and Rock Pigeon. The most common species were House Sparrow and Chilean Swallow. Total bird richness responds negatively to IS and MG, while native bird richness responds positively to NG and negatively to BD, IS DG and, RV. Total abundance increase in areas with higher values of DC and BD, and decrease in areas of higher values of IS, SW and VR. Native bird abundance responds positively to NG and negatively to BD, IS MG, DG and RV. Our results suggest that not all the general patterns described in previous studies, conducted mainly in the USA, Europe, and Australia, can be applied to Latin American cities, having important implications for urban planning. Conservation efforts should focus on non-municipal areas, which harbor higher bird diversity, while municipal green areas need to be improved to include elements that can enhance habitat quality for birds and other species. These findings are relevant for urban planning in where both types of green space need to be considered, especially non-municipal green areas, which includes wetlands, today critically threatened by urban development.     

城市绿地可达性与公平性评价

城市绿地是城市重要的绿色基础设施,是实现城市可持续发展的重要空间保障,具有重要的生态、社会文化功能.20世纪80年代以来,我国一直以城市人均(公共、公园)绿地面积、绿地率、绿化覆盖率等面积比率指标作为核心指标来指导城市绿地建设,缺乏具体引导城市绿地空间分布的指标,较少关注城市绿地服务功能的公平性问题.借助于GIS技术,构建了城市绿地社会功能评价的简明框架,尝试将表征城市绿地空间分布的可达性和公平性指标引入城市绿地的功能评价中,以体现城市建设"以人为本"、"社会公平"的理念,并以上海和青岛为实证,对新构建的系列指标进行了分析与检验.研究结果表明:(1)可达性和公平性系列指标导入城市绿地的功能评价中是可行的,能够有效的表征和测度城市绿地空间布局的合理性程度;(2)可达性和公平性指标使用时需要界定研究区范围、研究尺度,特别是数据精度,以利于研究区的纵向比较和城市间的横向比较.研究结果将丰富我国城市绿地评价的核心指标体系,亦可为城市规划者和建设者合理规划与布局城市绿地提供重要的依据和参考.     

Nature in the city,city in the nature: case studies of the restoration of urban nature in Tokyo,Japan and Toronto,Canada

Increasing demands for the restoration of nature in cities have led planners to seek an effective form, configuration and maintenance scheme for parks and open spaces in urban areas. This paper aims to introduce two contrasting examples of ways that planners have met the challenge of restoring nature in the city. It takes Tokyo Bay Bird Sanctuary Park (TBBSP), Tokyo, Japan, and Tommy Thompson Park (TTP), Toronto, Canada, as case studies. TBBSP is located on reclaimed land facing Tokyo Bay, and is surrounded by heavily industrialized areas. The absence of green corridors which connect TBBSP to surrounding green patches have turned TBBSP into an isolated oasis for migrating birds. TTP in Toronto is also located on reclaimed land facing Lake Ontario. However, TTP has become to be an indispensable green patch of the open space network of Toronto because it is located at the node of green corridors. The principles of landscape ecology may dictate that TTP, integrated in the green network of the area, is in far better condition than isolated TBBSP. However both case studies are based on the same early post-war parks and open space planning concept, which aimed to clearly separate urban greens from surrounding urban fabrics. To restore nature in cities it is important to understand that alternative models of parks and open space planning can exist. We therefore refer to the authentic urban pattern found in Japanese cities, which historically have not intended to clearly separate each land use types but have sustained a mix of open spaces and urban fabrics. In the context of the global concern to realize ecological cities, restoring a city by integrating greens in the urban fabric should be understood as a way of achieving a city in nature.     

Is urban green space per capita a valuable target to achieve cities’ sustainability goals? Romania as a case study

Urban green infrastructure is considered to be a key element in improving quality of life and creating an appropriate framework for sustainable cities. The most used quantitative indicator to assess urban green infrastructure is urban green space (UGS) per capita. This papeŕs aim is to analyze whether UGS is a valuable target to achieve cities’ sustainability goals. We used Romania as a case study, which should meet the target of 26 m² of UGS per inhabitants in all cities. Aerial images were used to extract the surface of the UGS categories for a sample of 38 cities in Romania. We compared our data with three other databases (National Institute of Statistics, Environmental Protection Agencies and Urban Atlas) to check for differences. To understand the contribution of geographic and socio-economic factors to the dynamic of the UGS per capita in Romania’s cities, we used a multiple linear regression. To identify differences between cities in terms of their proportions of UGS, multiple correspondence analysis was performed. We found significant differences between the surface of UGS reported by the administrative offices and that resulting from the spatial analysis. The process of reporting UGS data currently has methodological and perspective shortcomings. Moreover, the density of the built-up space, the proximity to major transport infrastructure, the cities’ founding period and the geomorphology criteria are important predictors for the UGS. The target of 26 m² of green area per inhabitant in all Romanian cities is not feasible and it should consider the cities’ characteristics, if you want to achieve sustainability goals. Urban green planning should focus more on the development of urban green infrastructure models that are adapted to each type of urban area.     

青岛市城市绿地生态系统的环境净化服务价值

在分析青岛市城市绿地空间分布及面积动态变化基础上,利用市场价值法、生产成本法、替代费用法等方法计算了1999-2009年各年度青岛市城市绿地生态系统的环境净化服务价值。结果表明,1999-2009年青岛市城市绿地的环境净化服务价值由1.587×10⁸元增至3.491×10⁸元,人均城市绿地的环境净化服务价值由68.42元增至126.73元。11a间青岛市城市绿地的环境净化服务价值增加了1.904×10⁸元,平均年增长率为10.91%。在青岛市城市绿地生态系统环境净化服务总价值构成中,其气体调节服务价值占总价值的49.81%- 51.72%,而吸收有害气体和滞尘服务价值、减弱噪声服务价值占48.28%-50.19%。城市绿地的气体调节服务具有地域空间的可转移性,可以由城市以外的自然生态系统补偿;而其吸收有害气体和滞尘服务与减弱噪声服务则不具有地域空间的可转移性。加强城市绿地建设、提高城市绿化水平是改善青岛市城市环境和提高城市居民生活质量的有效措施。     

The importance of blue and green landscape connectivity for biodiversity in urban ponds

The negative impact of urbanization on biodiversity can be buffered by blue (e.g., rivers, ponds) and green (e.g., parks, forests) spaces. However, to prevent biodiversity loss and reduce the risk of local extinctions, blue and green spaces need to be connected by corridors, so that organisms may disperse between sites. Landscape connectivity affects local community composition and metacommunity dynamics by facilitating dispersal. The goal of this study was to test the relative roles of pond environmental properties, spatial structure, and functional landscape connectivity on differentiation of invertebrate metacommunities in urban ponds in the city of Stockholm, Sweden. We characterized functional connectivity as blue connectivity (distance to water bodies), green connectivity (land use), and combined blue-green connectivity. We estimated functional connectivity by using electrical circuit theory to identify dispersal corridors. Interestingly, while circuit theory is often used in single-taxon studies, this method has rarely been applied to multiple taxa forming a metacommunity, as we have done in this study. Indeed, our study contributes toward an increased focus on the role of dispersal at the metacommunity level. We determined that functional connectivity was the most important factor in explaining community differentiation, with the local environment contributing comparatively little, and spatial structure the least. Combined blue-green functional connectivity had a major influence on structuring urban pond communities, explaining 7.8% of the variance in community composition across ponds. Furthermore, we found that increased functional connectivity was associated with an increase in the number of species. In summary, our results suggest that to preserve biodiversity in urban ponds, it is important to enhance functional connectivity, and that open green spaces could augment blue corridors in maintaining functional connectivity in urban pond metacommunities. To generalize these findings, future urban biodiversity studies should compare how functional connectivity affects metacommunities across multiple major cities.     

广州市典型绿地土壤水分入渗特征

绿地对于缓解城市洪涝灾害具有非常重要的作用,对其土壤入渗的定量化研究是评价城市绿地雨洪调蓄能力的关键。受城市土壤空间异质性的影响,不同功能区绿地土壤水分入渗速率的差异较大。采用双环入渗仪对广州海珠国家湿地公园典型乔草和灌草绿地的土壤水分入渗特征进行测定,并对其影响因素进行分析,结果表明：（1）广州海珠国家湿地公园的绿地土壤水分入渗性能处于中等至较高水平,但受机械和人为压实作用,绿地土壤容重偏大,总孔隙率偏低,加上外来客土影响,土壤物理性黏粒含量高,且有人为侵入体混入等,从而抑制了绿地表层土壤的水分入渗;（2）灌草相对于乔草对绿地表层土壤水分入渗的改善更为明显,这主要与前者的根系分布较浅有关,此外灌草绿地的凋落物更易留存,且其细根分解较快,这均有助于表层土壤有机质的及时返还,从而促进了绿地表层土壤的水分入渗;（3）广州海珠国家湿地公园绿地土壤的水分累积入渗量随时间变化更符合Kostiakov模型。未来广州市绿地的建设及管理应减少土壤压实及外来客土混入,适当增加灌草比例,使其兼顾旅游休闲和雨洪蓄积功能,从而有助于海绵城市的高效建设。     

Urban scaling and its deviations: revealing the structure of wealth, innovation and crime across cities

With urban population increasing dramatically worldwide, cities are playing an increasingly critical role in human societies and the sustainability of the planet. An obstacle to effective policy is the lack of meaningful urban metrics based on a quantitative understanding of cities. Typically, linear per capita indicators are used to characterize and rank cities. However, these implicitly ignore the fundamental role of nonlinear agglomeration integral to the life history of cities. As such, per capita indicators conflate general nonlinear effects, common to all cities, with local dynamics, specific to each city, failing to provide direct measures of the impact of local events and policy. Agglomeration nonlinearities are explicitly manifested by the superlinear power law scaling of most urban socioeconomic indicators with population size, all with similar exponents (1.15). As a result larger cities are disproportionally the centers of innovation, wealth and crime, all to approximately the same degree. We use these general urban laws to develop new urban metrics that disentangle dynamics at different scales and provide true measures of local urban performance. New rankings of cities and a novel and simpler perspective on urban systems emerge. We find that local urban dynamics display long-term memory, so cities under or outperforming their size expectation maintain such (dis)advantage for decades. Spatiotemporal correlation analyses reveal a novel functional taxonomy of U.S. metropolitan areas that is generally not organized geographically but based instead on common local economic models, innovation strategies and patterns of crime.